CD4 and female infertility: Recently, tacrolimus has been successfully prescribed in the preclinical management of PCOS-related female infertility in an obese murine model of PCOS [128] and in treating women without PCOS but with recurrent implantation failure (RIF)/recurrent pregnancy loss (RPL) with elevated systemic Th1 (CD4+ IFNγ+):Th2 (CD4+IL4+) cell ratios [129].